Stem cells are defined by the ability to continuously self-renew and produce the differentiated progeny of the tissue of their location (Morrison et al., 1997). Adult stem cells are undifferentiated cells that reside in differentiated tissues, and have the properties of self-renewal and generation of differentiated cell types. The differentiated cell types may include all or some of the specialized cells in the tissue. Sources of stem cells include bone marrow, blood, the cornea and the retina of the eye, brain, skeletal muscle, dental pulp, liver, skin, the lining of the gastrointestinal tract, and pancreas. Adult stem cells make up a small percentage of the total cells. For instance, in the small intestine there are perhaps up to 10 stem cells at the bottom of the crypt out of a total crypt population of <300 cells. In skeletal muscle, satellite (stem) cells comprise about 5% of all nuclei, but in the bone marrow the multi-potential hematopoietic stem cell is much rarer, with a frequency of perhaps 1 in 10000 amongst all bone marrow cells. Considerable overlap exists between different putative organ specific stem cells in their repertoire of gene expression, often related to self-renewal, cell survival, and cell adhesion. However, the conditions to grow or simply ‘select’ stem cells in vitro do not exist for many tissues where it is accepted that the stem cells simply fail to grow due to lack of required growth factors or substrates. In many tissues, the stem cells have simply not been identified.
Nevertheless stem cells have been used routinely for more than three decades to repair tissues and organs damaged by injury or disease. While early, embryonic stem cells have generated considerable interest, adult stem cells are critical for tissue homeostasis and wound repair and reside within specific niches that preserve proliferative and regenerative potential (Blanpain and Fuchs, 2006; Moore and Lemischka, 2006).
Thus, understanding how stem cells are maintained, stimulated and participate in regeneration is important to combat a wide variety of diseases.
Stem cell therapy is a type of intervention strategy that introduces new adult stem cells into damaged tissue in order to treat a disease or an injury. Many medical researchers believe that stem cell treatments have the potential to change the face of human disease and alleviate suffering. The ability of stem cells stem to self-renew and give rise to subsequent generations with variable degrees of differentiation capacities offers significant potential for generation of tissues that can potentially replace diseased and damaged areas in the body, with minimal risk of rejection and side effects.
Today, a number of stem cell therapies exist, but most are only at experimental stages or is costly. But, medical researchers anticipate that stem cell therapy will probably be able to treat cancer, type 1 diabetes, Parkinson's disease, Huntington's disease, Celiac Disease, cardiac failure, muscle damage and neurological disorders, and many others. Nevertheless, before stem cell therapeutics can be applied in the clinical setting, more research is necessary to understand stem cell behavior upon transplantation as well as the mechanisms of stem cell interaction with the diseased/injured microenvironment.
For over 30 years, bone marrow, and more recently, umbilical cord blood stem cells, has been used to treat cancer patients with conditions such as leukemia and lymphoma. During chemotherapy, most growing cells are killed by the cytotoxic agents. These agents, however, cannot discriminate between the leukemia or neoplastic cells, and the hematopoietic cells within the bone marrow. It is this side effect of conventional chemotherapy strategies that the stem cell transplant attempts to reverse in that a donor's healthy bone marrow reintroduces functional stem cells to replace the cells lost in the host's body during treatment.
In the following, a number of known treatments are discussed.
Stroke and traumatic brain injury lead to cell death, characterized by a loss of neurons and oligodendrocytes within the brain. Healthy adult brains contain neural stem cells which divide to maintain general stem cell numbers, or become progenitor cells. In healthy adult animals, progenitor cells migrate within the brain and function primarily to maintain neuron populations for olfaction (the sense of smell). In pregnancy and after injury, this system appears to be regulated by growth factors and can increase the rate at which new brain matter is formed. Although the reparative process appears to initiate following trauma to the brain, substantial recovery is rarely observed in adults, suggesting a lack of robustness.
Stem cells may also be used to treat brain degeneration, such as in Parkinson's and Alzheimer's disease.
The development of gene therapy strategy for treatment of intra-cranial tumors offers much promise, and has shown to be successful. Using conventional techniques, brain cancer is difficult to treat because it spreads so rapidly. Researchers at the Harvard Medical School transplanted human neural stem cells into the brain of rodents that received intracranial tumors. Within days, the cells migrated into the cancerous area and produced cytosine deaminase, an enzyme that converts a non-toxic pro-drug into a chemotherapeutic agent. As a result, the injected substance was able to reduce the tumor mass by 81 percent. The stem cells neither differentiated nor turned tumorigenic—Some researchers believe that the key to finding a cure for cancer is to inhibit proliferation of cancer stem cells. Accordingly, current cancer treatments are designed to kill cancer cells. However, conventional chemotherapy treatments cannot discriminate between cancerous cells and others. Stem cell therapies may serve as potential treatments for cancer. Research on treating Lymphoma using adult stem cells is underway and has had human trials. Essentially, chemotherapy is used to completely destroy the patient's own lymphocytes, and stem cells injected, eventually replacing the immune system of the patient with that of the healthy donor.
Successful immune modulation by cord blood stem cells and the resulting clinical improvement in patient status may have important implications for other autoimmune and inflammation-related diseases.
However, there is still a need to better use stem cell therapy for curing diseases and other disorders. For this purpose, apparatus such as lasers have been used.
The use of lasers within science and medicine for the treatment of diseases, in particular the above mentioned diseases, and in therapy is currently widespread. Many researchers and research groups are performing experiments concerning tissue reactions in vitro in order to survey, predict and explain the effects of laser irradiation. Other researchers carry out tests in vivo on animals. Clinical research and clinical treatment have also been documented.
Therapeutic lasers used in medicine, for instance for stem cell therapy, generally fall into two categories: non-destructive, low-energy lasers, also referred to as “cold lasers” designed to generate largely thermal biological effects in tissue, and destructive lasers designed to selectively damage or destroy tissue.
The first category of laser, referred to as cold laser or low-level laser, typically use very low power density or irradiation. These low level lasers are used, for example, in laser therapy for stimulating cellular processes that are important in cellular regeneration and repair. Typically, a low level laser is designed to work through photochemical mechanisms and cause almost imperceptible changes in the temperature of the cells subject to such lasers. In essence, until now, low level lasers have only been used for thermal medical treatment. Typical maximum effective irradiances are within the range of about 1-45 mW/cm2. Above this range a biological effect dose-response is often reported to be negative.
The second type of laser, the destructive so-called “high-level laser” will not be described in more detail herein this disclosure.
Treatment with low level lasers will not be discussed in more detail here, and the reader is referred to scientific studies and similar, such as “Isolated Neuron Response to Blue Laser Micro irradiation: Phenomenology and Possible Mechanism”, A. B. Uzdensky, Department of Biophysics and Bio cybernetics, Physical Faculty, Rostov State University, Stachky av., 194/1, Rostov-on-Don. 344090, Russia and Rochkind S. (1992) “Spinal Cord and Brain transplantation benefited by low-power laser irradiation”. Lasers in Medical Science 7: 143-115.
Typically, a therapist who performs a low level laser treatment has many years of experience and must know where to apply radiation to tissue and how much to apply, for example, with respect to the power of the laser measured in milliwatts (mW), and which wavelength of light is most suitable for different types of treatment. This may be troublesome since there is often a need for sufficiently trained and experienced therapists. Even a very experienced therapist may suffer from sufficient training and experience to be able to control the laser probe properly.